In past work, we have established that infrared thermography is technically possible in the mouth. However, there have been indications in these studies that the infrared emissivity of teeth and oral mucosa is markedly less than unity. Skin thermographers justifiably ignore emissivity, since the emissivity of skin approaces unity. However, since the infrared radiation of tissue in the mouth is proportional not only to temperature but also to less than unity emissivity, it is necessary to determine intraoral emissivity values before valid clinical thermography can be accomplished in the mouth. In addition, there is the possibility that emissivity itself, as distinguished from temperature, changes as a result of disease process. The present study is designed to determine intraoral emissivity values and how these values are affected by disease processes.